This invention relates to a fluorescent luminous device including cathodes and a plurality of anode dots, and more particularly to a fluorescent luminous device effectively available as a printer head for optical writing, a graphic display device for displaying any desired characters or figures and the like. When the fluorescent luminous device of the present invention is used as a printer head, it may be commonly applied to various kinds of optical printers for writing on a photosensitive drum, writing on a photosensitive film and the like.
Now, a conventional fluorescent printer head will be described with reference to FIG. 11. A conventional fluorescent printer head generally designated at reference numeral 100 includes an anode substrate 102 constituting a part of an envelope, which anode substrate is provided thereon with two anode chains 107 and 108 each constituted of a plurality of anode dots 106. The anode dots 106 of the anode chain 107 and those of the anode chain 108 are arranged in an offset manner with respect to each other. The respective two anode dots 106 of the anode chains 107 and 108 obliquely opposite to each other and adjacent to each other are connected together and led out to one side of the anode chains 107 and 108, resulting in being connected to an IC acting as an anode drive means. The fluorescent printer head 100 also includes a first cathode 112 and a second cathode 113 stretchedly arranged above the anode chains 107 and 108, respectively. Further, the fluorescent printer head 100 includes a shield electrode 120 arranged between the anodes chains 107 and 108, as well as a first control electrode 130 and a second control electrode 131 respectively arranged outside the first and second cathodes 112 and 113, with the cathodes 112 and 113 and shield electrode 120 being interposed between the first control electrode 130 and the second control electrode 131. The shield electrode 120 has a positive voltage constantly applied thereto. The respective two anode dots 106 of the anode chains 107 and 108 obliquely opposite to each other are driven in order by the IC. In synchronism with the driving, the control electrode 130 or 131 has a selection signal fed thereto. When this results in the first control electrode 130 being selected, electrons are permitted to enter between the first control electrode 130 and the shield electrode 120, to thereby impinge on the anode dots 106 of the anode chain 107 to which a drive signal is fed. In this instance, the second control electrode 131 has a negative voltage applied thereto to form an electric field, which prevents electrons emitted from the second cathode 113 from impinging on the anode dots 106.
Thus, in the conventional fluorescent printer head 100 thus constructed, it is required that the first and second control electrodes 130 and 131 which are constructed so as to be controlled independently from each other are arranged for the respective anode chains 107 and 108 in order to select the anode chains. Also, the conventional fluorescent printer head 100 requires a power supply for applying a negative potential to each of the first and second control electrode 130 and 131.
Also, in order to increase an anode potential to enhance luminance in the conventional fluorescent printer head 100, it is required to increase a negative potential of the non-selected control electrode to prevent leakage luminescence of the non-selected selected anode chain. Further, this requires to increase a capacity of the power supply for negative potential application.
In addition, an increase in negative potential of the non-selected control electrode by increasing an anode potential causes a potential difference between the anode an the control electrode to be highly increased. However, in the fluorescent printer head 100, the control electrodes 130 and 131 and anode wirings are arranged in proximity to each other in a vertical direction so as to be spaced from each other at a distance as small as 10 to 20 xcexcm, so that an increase in potential difference therebetween causes dielectric breakdown to readily occur in the envelope.
The present invention has been made in view of the foregoing disadvantage of the prior art.
Accordingly, it is an object of the present invention to provide a fluorescent luminous device which is capable of eliminating arrangement of independently controllable control electrodes and a power supply for applying a negative potential to the control electrodes.
It is another object of the present invention to provide a fluorescent luminous device which is capable of being small-sized and reduced in manufacturing cost.
It is a further object of the present invention to provide a fluorescent luminous device which is capable of minimizing dielectric breakdown between electrodes.
In accordance with the present invention, a fluorescent luminous device is provided. The fluorescent luminous an anode substrate and an anode including a plurality of anode chains each constituted of a plurality of anode dots arranged so as to be spaced from each other at predetermined intervals on the anode substrate. The anode dots of the anode chains which correspond to each other are connected together. The fluorescent luminous device also includes an anode drive means for driving the anode dots of the anode, cathodes arranged above the anode chains, respectively, and a cathode selection means for applying a voltage to the cathodes independently from each other to select the anode chains.
In a preferred embodiment of the present invention, the cathode selection means applies a positive potential to the cathodes non-selected and a zero or negative potential to the cathodes selected.
In a preferred embodiment of the present invention, the fluorescent luminous device further includes a shield electrode arranged between each two of the cathodes so as to separate spaces above the anode chains from each other. The shield electrode has a zero or positive potential applied thereto.
In a preferred embodiment of the present invention, the fluorescent luminous device further includes a cut-off electrode having a potential lower than a positive potential which is applied to the cathodes applied thereto.
In a preferred embodiment of the present invention, the positive potential applied to the cathodes is lower than a positive potential applied to the anode.
In a preferred embodiment of the present invention, the fluorescent luminous device further includes a shield electrode arranged between each two of the cathodes so as to separate spaces above the anode chains from each other and a cut-off electrode for preventing electrons from being discharged from the non-selected cathodes to the anode chains corresponding thereto. The shield electrode and cut-off electrode are integrally constructed so as to cover the cathodes and have a potential lower than a positive potential which is applied to the cathodes applied thereto.